On Fri, Apr 22, 2011 at 2:20 AM, Rajkumar Manoharan
<rmanoharan@xxxxxxxxxxx> wrote:
> On AR9003 chips, doing three IQ calibrations will possibly cause chip
> in stuck state. In noisy environment, chip could receive
> a packet during the middle of three calibrations and it causes
> the conflict of HW access and the eventual failure. It also
> causes IQ calibration outliers which results in poor Tx EVM.
[...]
> + /* find min/max mismatch across all calibrated gains */
> + for (i = 0; i < nmeasurement; i++) {
> + mp_avg += mp_coeff[i];
> + if (mp_coeff[i] > mp_max) {
> + mp_max = mp_coeff[i];
> + max_idx = i;
> + } else if (mp_coeff[i] < mp_min) {
> + mp_min = mp_coeff[i];
> + min_idx = i;
> + }
> + }
>
> - if (diff[0] <= diff[1] && diff[0] <= diff[2])
> - *mp_avg = (mp_coeff[0] + mp_coeff[1]) / 2;
> - else if (diff[1] <= diff[2])
> - *mp_avg = (mp_coeff[1] + mp_coeff[2]) / 2;
> - else
> - *mp_avg = (mp_coeff[2] + mp_coeff[0]) / 2;
> + /* find average (exclude max abs value) */
> + for (i = 0; i < nmeasurement; i++) {
> + if ((abs(mp_coeff[i]) < abs(mp_max)) ||
> + (abs(mp_coeff[i]) < abs(mp_min)))
Doesn't this potentially throw away more than one potential sample
from your mp_avg sum if more than one value has the same (maximal
absolute) value? You don't account for it below since you divide by
(nmeasurement - 1) so your average can get arbitrarily smaller than
you intended, which may false-trigger your outlier detection.
> + mp_avg += mp_coeff[i];
> + }
> + mp_avg /= (nmeasurement - 1);
>
> - return true;
> + /* detect outlier */
> + if (abs(mp_max - mp_min) > max_delta) {
> + if (abs(mp_max - mp_avg) > abs(mp_min - mp_avg))
> + outlier_idx = max_idx;
> + else
> + outlier_idx = min_idx;
> + }
> + mp_coeff[outlier_idx] = mp_avg;
> }
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